Nowadays, TFT-LCDs (liquid crystal display) are commonly being applied to various electronic apparatus of information technology, such as monitors for personal computers, displays for notebook computers. That is, a TFT-LCD module consisting of a TFT-LCD panel, driving-circuit unit, backlight system, and assembly unit is commonly used to display characters and graphic images when connected a host system, wherein the TFT-LCD panel consists of a TFT-array substrate and a color-filter substrate. Moreover, The TFT-array substrate contains the TFTs, storage capacitors, pixel electrodes, and interconnect wiring, and the color filter contains the black matrix and resin film containing three primary-color—red, green, and blue—dyes or pigments. In this regard, the operation of the TFT-LCD is based on the use of the TFTs to actuate the pixel electrodes.
Therefore, the thin film transistor (TFT) plays an important role while fabricating a liquid crystal display (LCD). A conventional thin film transistor, especially a bottom-contact organic thin film transistor, has pixel electrodes fabricated by the photolithography process, which is capable of defining channel length easily, but have to go through a plurality of steps of exposing, developing, etching, and photoresist removing, etc. Hence, it is desired to reduce the steps of fabricating the thin film transistor for the LCD.
For example, a method of fabricating a thin film transistor is disclosed in R.O.C. Patent No. 518682 with reference to FIG. 1A to FIG. 1C. As seen in FIG. 1A to FIG. 1C, the method of fabricating the thin film transistor comprises the following steps:                a) providing a substrate 10 while forming a gate electrode 12 thereon;        b) coating a first dielectric layer 14 on the substrate 10 and the gate electrode 12 completely, and then coating a backfill dielectric layer 16 on the first dielectric layer 14;        c) etching the backfill dielectric layer 16 via plasma etching till the backfill dielectric layer 16 on the gate electrode 12 is completely removed, and consequently, forming a pair of patterning backfill dielectric layers 16a, 16b;         d) forming a patterning third dielectric layer 20 on an exposure portion of the first dielectric layer 14 and the pair of patterning backfill dielectric layers 16a, 16b, and further forming a patterning active semiconductor layer 22 aligning with the patterning third dielectric layer 20; and        e) forming a pair of patterning ohmic contact layers 24a, 24b contacting each other respectively on the two end points of the patterning active semiconductor layer 22, and further forming a pair of patterning conducting layers 26a, 26b on the patterning ohmic contact layers 24a, 24b while respectively aligning with the same, wherein the patterning conducting layers 26a, 26b are employed as electrodes (drain/source).        
Though a reliable thin film transistor structure may be fabricated through the above method, steps (exposing, developing, etching and photoresist removing) of the photolithography process are still complicated. Furthermore, when the insulation layer is made of an organic material, it is inconvenient to fabricate the patterning organic electrodes and it tends to be restricted by the material. When the electrodes are fabricated via printing, it is inconvenient to align.